1. Field of the Invention
The present invention relates mainly to an apparatus which estimates the state of an object by using a particle filter.
2. Description of the Related Art
In order to improve the accuracy of tracking an object by using a particle filter, there has been proposed a technique in which a plurality of motion models, each of which matches each of a plurality of motion characteristics of the object, is prepared for an entire set of particles, and these plural motion models are adaptively changed (refer to Japanese Patent Application Laid-Open No. 2007-328746).
However, each particle is displaced according to each of the plurality of models corresponding thereto at each particular time, and then the likelihood relative to an observation result is calculated to select one model owned by a group of particles having a higher likelihood among the plurality of models, thereby tracking the object. In other words, the same number of likelihoods relative to the observation results as the number obtained by multiplying the number of particles by the number of models at each particular time is calculated. This is inefficient, because the arithmetic processing volume required for tracking the object inevitably becomes enormous. On the other hand, if the number of particles is decreased to reduce the arithmetic processing volume, then the object tracking accuracy is likely to deteriorate.